This invention pertains to gas turbine power producing plants incorporating fuel rich-lean burn topping combustors that require control of the rich-lean burn zone temperatures to minimize the combustor emissions of nitrogen oxides and carbon monoxide from the combustor. It pertains particularly to second-generation pressurized fluidized bed combustor power plants in which a rich-lean burn topping combustor unit is used to burn a fuel gas with vitiated air (an air-flue gas mixture) for gas turbine power output.
Topping combustor units used in pressurized fluidized bed combustion processes for producing power are generally known. For example, U.S. Pat. No. 4,787,208 to DeCorso discloses a low-NOx rich-lean combustor suitable for use with a combustion gas turbine. U.S. Pat. No. 4,845,940 to Beer discloses a low-NOx rich-lean combustor containing concentric annular passages and useful in gas turbines. U.S. Pat. No. 5,161,367 to Scalzo discloses a coal-fired gas turbine system with an internal topping combustor; U.S. Pat. No. 5,218,815 to Korenberg discloses a gas turbine power cycle which burns solid fuel such as coal in a carbonizer and a char combustor in combination with a topping combustor upstream of the gas turbine to produce shaft power. Also U.S. Pat. No. 5,255,506 to Wilkes et al; and U.S. Pat. No. 5,261,226 to Pillsburg each disclose gas turbine power systems which utilize topping combustors. However, further improvements to such combustion units are needed so as to achieve reduced NOx and CO emissions and provide increased thermal efficiency and reduced costs for solid fuel combustion power generating plants.